1. Field of the Invention
This invention relates to conveyor systems. More particularly, it relates to conveyors for printed circuit assemblies which traverse inclines. Such conveyor systems are often utilized in connection with solvent baths used for cleaning printed circuit boards following a wave soldering operation.
2. Description of the Related Art
Conveyor systems used to transport printed circuit assemblies (PCA's) into and through solvent cleaning baths typically employ conveyor belts having an open mesh design. This design permits the solvent to contact nearly 100% of all surfaces of the PCA when it is immersed in the solvent bath thereby providing a more thorough cleaning than would be possible if an impervious conveyor belt were used.
One such conveyor belt or chain is shown as 10 in FIG. 1. The conveyor chain illustrated is Part No. 1329 (from Wire Belt Company of America, Winchester, Mass. for the Baron-Blakeslee cleaner Model CBL-18 (Baron-Blakeslee Division, Allied-Signal, Inc., Chicago, Ill. It comprises an interlocked set of stainless steel links which form an endless belt. The conveyor chain is arranged in a loop configuration within an automatic solvent cleaning apparatus for PCA's. The conveyor chain is additionally equipped with clip-on wire bails 12 which segment the chain into "flights". The length of the flights can be selected by varying the positions of the wire bails.
Inasmuch as the conveyor chain travels up and down inclines as it moves PCA's into and out of the solvent bath or solvent cleaning section of the apparatus, it is necessary to equip the conveyor chain with the above-described wire bails to provide a positive stop for the PCA's. Without such stops, the PCA's could slide on the inclined portions of the conveyor and either stop moving through the apparatus altogether or jam the mechanism.
It will be appreciated by those skilled in the art that the wire bails 12 must be placed so as to accommodate the longest PCA's that will be placed on the conveyor chain. As a result, shorter PCA's can slide on the conveyor chain between the leading wire bails and the following set of bails which defines the next flight. Such sliding has been found to damage leads which project on the underside of the PCA's as well as components mounted on that side of the printed circuit board. Given the trend towards ever higher circuit densities, designers are placing more and more components on the "solder side" of printed circuit boards. As a result, the likelihood of damage occurring when a PCA slides on the surface of a conveyor chain increases for high density circuit boards. The present invention solves this problem.